Fix failure to request stddev of non-intrinsics

Before this fix, the code would fail if only standard deviations of
extrinsic parameters are requested. While standard deviations matrix
should be computed if any set of standard deviations is requested. A
variable is added to represent this case.

modules/calib3d/src/calibration.cpp

@@ -3426,7 +3426,8 @@ double cv::calibrateCamera(InputArrayOfArrays _objectPoints,
             tvecM = _tvecs.getMat();
     }
 
-    if( stddev_needed || stddev_ext_needed )
+    bool stddev_any_needed = stddev_needed || stddev_ext_needed;
+    if( stddev_any_needed )
     {
         stdDeviationsM.create(nimages*6 + CV_CALIB_NINTRINSIC, 1, CV_64F);
     }
@@ -3447,7 +3448,7 @@ double cv::calibrateCamera(InputArrayOfArrays _objectPoints,
                                           &c_cameraMatrix, &c_distCoeffs,
                                           rvecs_needed ? &c_rvecM : NULL,
                                           tvecs_needed ? &c_tvecM : NULL,
-                                          stddev_needed ? &c_stdDev : NULL,
+                                          stddev_any_needed ? &c_stdDev : NULL,
                                           errors_needed ? &c_errors : NULL, flags, cvTermCriteria(criteria));
 
     if( stddev_needed )